Contention when multiple threads access one dll

[hotchickneedshelp]

I have a custom created C++ dll that is running on a Windows NT 4.0 Server. The one dll is accessed by multiple users (approx. 50). We have not included code to handle multiple threads accessing that server. We are running into contention problems that I believe might be due to the fact that one dll is used. Has anyone seen this before and can they provide additional insight?

Thanks!
Hot Chic